An oil pump provided in a vehicle engine is powered by a balancer shaft located underneath a crankshaft and a plurality of cylinders of the engine. The balancer shaft, receiving rotational power from a gear drive attached to the crankshaft, joins with a portion of the oil pump via a meshing connection. When the engine is operating, the oil pump is also operated to pressurize oil located in a sump of the engine (i.e., oil pan). The pressurized oil is routed through a number of passages located throughout the engine for providing cooling and/or lubrication to the engine and its components. During the engine's lifetime, the oil pump may be periodically serviced and/or replaced. As such, the inventors herein have recognized that it is desirable to provide a support structure of the oil pump that allows for simple removal of the oil pump from the engine to save cost and time.
In a structure for an oil pump shaft and a balancer shaft, shown by Endo et al. in U.S. Pat. No. 6,758,183, a crankshaft provides power to the oil pump via a number of connections and shafts. A driving sprocket is fixed on the crankshaft while an endless chain connects the driving sprocket to a driven sprocket fixed on an input-side balancer shaft. Rotation force of the crankshaft is transmitted from the input-side balancer shaft to an output-side balancer shaft via gears so an oil pump shaft can rotate. In this embodiment, the two balancer shafts are located side-by-side and the oil pump is mounted to the oil pump shaft which is collinear with the output-side balancer shaft. Due to the proximity of the driven sprocket, various shafts, and the oil pump, when assembled the driven sprocket and other components are positioned in front of the oil pump. The other components include a tensioning system with a tensioner body, a shoe, and a tubular oil conduit. The components, located at the end of the balancer shafts, are adjacent to the oil pump such that the oil pump is sandwiched against the oil pump shaft (connected to the output-side balancer shaft).
However, the inventors herein have identified potential issues with the oil pump structure of U.S. Pat. No. 6,758,183. If the oil pump needs to be removed from the engine to be serviced or replaced before other components such as the shafts need to be replaced, then the structure may hinder the removal process. In particular, parts of the balancer shaft assembly and associated components may need to be disassembled prior to removing the oil pump. For example, the driven sprocket, tensioning system, and endless chain may be unfastened and removed prior to pulling the oil pump from the oil pump shaft. This process may increase the amount of time and serviceability cost associated with replacing or otherwise repairing the oil pump. Furthermore, while reinstalling the oil pump, the tensioning system will also be reinstalled, which may require careful tightening of the endless chain as well as adjustment of other tensioning components. As such, periodical servicing of the oil pump may be more expensive, difficult, and time-consuming than other systems that provide easier access to the oil pump.
Thus in one example, the above issues may be at least partially addressed by a system, comprising: an oil pump with a drive end that meshes with a balancer shaft inside a fully enclosed support structure, wherein the drive end fixedly rotates with the balancer shaft; and a plurality of dowel bolts fixing and aligning the oil pump to an engine frame, wherein a substantially flat bottom surface of the oil pump has face-engaging contact with a substantially flat top surface of the engine frame. In this way, the oil pump may be serviced or replaced while reducing the number of components also removed from the engine during the servicing. In a similar sense, putting the oil pump back into the engine is also made easier. Each of the dowel bolts comprise an unthreaded shank, a dowel portion, and a threaded portion such that the dowel portion only partially inserts into both the oil pump and engine frame to provide alignment while the threaded portion meshes with threads of a tapped hole located in the engine frame. By removing the dowel bolts, sliding the oil pump axially, then lifting the oil pump from the engine in a transverse direction, the oil pump can be removed from the engine without removing other components such as the balancer shaft.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.